This application is a continuation of PCT Application No. PCT/EP02t00604 filed Jan. 23, 2002, which claims priority to German Patent Application No. 101 05 542.0 filed on Feb. 7, 2001.
The invention relates to a lubricating oil supply system for the connecting rod bearings of a crankshaft of a multi-cylinder internal-combustion engine, in which oil ducts extend from bearing journal to crank pins of the crankshaft, and in which oil supply taking place by way of main bearings of the crankshaft. The oil ducts extend from one main bearing or bearing journal respectively to the crank pins or connecting rod bearings in each case adjoining on both sides.
German Patent Document DE 696 05 567 T2 illustrates a crankshaft for a 4-cylinder in-line engine in the case of which, by way of the bearing journals or main bearings of the crankshaft, the lubricating oil supply to the crank pins or connecting rod bearings adjoining the main bearing on both sides takes place by way of oil bores made in the crankshaft. The central main bearing can remain free of oil supply bores or oil supply grooves as a result of supplying lubricating oil to two connecting rod bearings respectively by way of a crankshaft main bearing.
It is also known (see, for example, French Patent Document FR-PS 979 586) to provide partial oil supply grooves in the main bearing shells of the crankshaft. The partial oil supply grooves are arranged in a deviated manner with respect to the gas force plane. By way of two oil bores provided in the bearing journal of the crankshaft, a permanent lubricating oil supply to the connecting rod bearing can be ensured by way of the partial oil supply grooves. Simultaneously, the bearing fraction of the main bearing can be maintained in the direction of the gas force plane.
It is an object of the invention to provide a lubricating oil supply system for the connecting rod bearings of a crankshaft of a multi-cylinder internal-combustion engine in which, on the one hand, a secure and reliable lubricating oil supply to the connecting rod bearings of the crankshaft is ensured and, on the other hand, the main bearings of the crankshaft, which are more stressed, particularly in the high rotational speed range, can securely absorb the gas forces and inertia forces.
This object is achieved by providing a lubricating oil supply system of the type mentioned in which, in respective bearing journals of the crankshaft for the lubricating oil supply to the connecting rod bearings adjoining on the left and right, respectively, two oil bores respectively are provided. The two oil bores extend at an angle and, converging to a third oil bore, extend to two adjoining crank pins. The two oil bores interact with oil supply grooves provided in the main bearings for lubricating oil supply.
In a 6-cylinder opposed-cylinder engine with a 120° spark gap, it was found that, starting at a certain rotational speed level, the bearing forces acting upon the main bearings, in which the oscillating inertia forces transmitted on the left and on the right by the crank pins are not compensated, will clearly rise. At the same time, the bearing forces in the main bearings, whose adjoining pair of crank pins is mutually offset by a crank angle of 180°, remain essentially constant independently of the rotational speed because of the compensation of the oscillating inertia forces. The suggested lubricating oil supply concept for the connecting rod bearings takes this circumstance into account. The same width can simultaneously be maintained for all main bearings despite different bearing loads.
In order to maintain the bearing fraction of the main bearings responsible for the lubricating oil supply, it is suggested to provide these main bearings only with partial oil supply grooves which interact with two oil bores respectively provided in the bearing journal. Consequently, alternatingly, by way of one oil bore, respectively, a continuous lubricating oil supply to the connecting rod bearings is ensured. In this case, the oil supply grooves are arranged to deviate by approximately 90° with respect to the gas force plane so that the bearing fraction of the main bearings in the direction of the applied main forces is not reduced.
The following description and the claims contain additional advantageous further developments and improvements of the lubricating oil supply system for the connecting rod bearings of a crankshaft.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.